1. Field of the Invention
The present invention relates to an alternator for use in a vehicle, and in particular relates to an alternator being suitable to be mounted on a vehicle, such as an automobile, etc.
2. Description of Prior Art
An A-C power generator for use in a vehicle, which is called by an alternator, is generally driven by an engine of the vehicle, such as, an internal combustion engine, for supplying electric power or energy for various automobile appliances within a car, and ordinarily, it is driven by means of a belt which is wound around a pulley attached onto a driving shaft of the internal combustion engine. Though a rotation speed of the internal combustion engine changes variously, conduction current flowing into an excitation coil is so adjusted that the voltage generated by the alternator comes to be constant, because of the necessity of a constant voltage of, such as 12V or the like, for example, which must be supplied to those automobile appliances. Current flows through the excitation coil, as well as, through a stator coil, a rectifier and a voltage regulator of the alternator for use in the vehicle, during electric power generation, and therefore it also causes heat generation therein, of course. Accordingly, it is necessary to cool down them compulsively, so as not to be overheated.
Conventionally, for the purpose of removing or taking away such the heat generated therein, an air outside is introduced into a room or space defined around a rotor by means of a cooling fan(s), which is/are provided at a front or/and rear of the rotor in the axial direction thereof, thereby achieving air-cooling thereof, however accompanying with an increase in the consumption of electric power by the automobile appliances for the vehicle, a further increase is demanded on a power output of the alternator for use in the vehicle, and it comes very difficult to obtain a cooling effect sufficiently, only by such means as the cooling fan(s) mentioned above. Also, since an amount of ventilation by the cooling fan(s) must be enlarged, in such the case of cooling by such the means of the cooling fan(s), large noises, which are caused by the fact that the cooling fan(s) rotates, leak out into an outside thereof. It is well known that the noises caused by such the wind power rise up in proportional to sixth power of the rotation speed. The noises caused by the cooling fan(s) rotating at high speed come to uncomfortable sound for the driver of an automobile.
Then, the alternator for use in a vehicle according to the conventional art comprises, as shown in Japanese Patent Laying-Open No. 2000-83351 (Conventional Art 1), for example: a rotation shaft onto which the rotational torque is transmitted from the engine of the vehicle through a pulley; a rotor being fixed onto the rotation shaft and exited by an excitation coil; a stator being provided outside an outer periphery of the rotor; a front bracket for supporting the stator in an axial direction of the rotor from a side of the pulley and for supporting the rotation shaft through a front shaft bearing, being formed with passages for cooling liquid or coolant therein; a rear bracket for supporting the stator from the side opposing the pulley and for supporting the rotation shaft through a rear shaft bearing, being formed with passages for the coolant therein; and a housing being formed with passages for the coolant, so as to connect between the passages for the coolant in the front bracket and the rear bracket. And, the housing is so provided that it encloses or cover all around the stator, and it has the passages formed, including an outward way located in an upper part and a return way located in a lower part, wherein each of the passages for coolant formed in the front bracket and the rear bracket has a diameter nearly equal to that of the passages of this housing, and is extended in a peripheral direction thereof. Also, the front and rear brackets are thermally connected to the rotor, the stator, the rectifier and the voltage regulator, etc., but being electrically insulated therebetween. Furthermore, the rotor is in the condition of being closed or shut off by the front and rear brackets at the both ends thereof. In this manner, the cooling capacity can be enlarged or enhanced by means of those passages for the coolant, which are provided in the brackets, and therefore it is possible to obtain a higher power output there from, comparing to the conventional structure having only the cooling fan(s), and to prevent the noises generated from the rotor side from leaking out into an outside, as well, because of the structure hermetically enclosing the rotor therein.
Also, the alternator for use in a vehicle according to the conventional art comprises a cooling structure of both air-cooling system and liquid-cooling system, as shown in Japanese Patent Laying-Open No. Hei 7-194060 (1995) (Conventional Art 2), for example, wherein the air-cooling system is built up with cooling fans, which are fixed on the front and rear surfaces of a pole core, and an air gap defined between an outer peripheral surface of the rotor and inner surfaces of the front and rear brackets, while the liquid-cooling system with a flow passage for use in cooling the rectifier, a flow passage for use in cooling the voltage regulator, a tube for use in cooling peripheral surfaces of the coil, and a tube for use in cooling rear surface of the coil, which are provided in parallel. And, in the air-cooling system by means of the cooling fans fixed on the front surface of the pole core, the cooling fan is rotated around, thereby sucking the air outside from an intake opening, so as to discharge it from an outlet opening after circulating the air within the gap. Also, in the air-cooling system by means of the cooling fans fixed on the rear surface of the pole core, the cooling fan is rotated around, thereby mixing and circulating the air within the gap in the encloses structure.
However, according to the conventional art 1, since the rotor must be constructed to be hermetically enclosed accompanying with the provision of the passages for coolant, it cannot be cooled down sufficiently, thereby bringing about an increase in temperature of the excitation coil thereof, and therefore a problem occurs that it is difficult to obtain a further increase in the power output of the alternator.
On the other hand, according to the conventional art 2, it is tried to enhance the cooling capacity of the rotor by means of the cooling fans, as well as, to conduct the cooling of the stator and the electric appliances (e.g. the rectifier, the voltage regulator, etc.) by the liquid-cooling, by combining the liquid-cooling system and the air-cooling system, however in the example of the air-cooling system by means of the cooling fan fixed on the front surface side of the pole core, since the fan builds up an open-type of sucking the air outside into, a problem occurs that the noises generated in the rotor side, including the cooling fan, leaks out into the outside thereof. While, in the example of the air-cooling system by means of the cooling fan fixed on the side of rear surface of the pole core, since the air is only mixed up and circulated within the gap of the hermetically closed structure, it is difficult to obtain sufficient cooling capacity, therefore bringing about a problem that it is difficult to obtain a further increase in the power output of the alternator.
Furthermore, due to the demand upon small-sizing of a car in recent years, the alternator for use in the vehicle is located, so that various parts or components come close to the surrounding of the place where it is installed, in various modes, thereby being extremely restricted in a space where the alternator can be installed. On the other hand, it is also necessary to improve mass-productivity thereof, by standardization of the alternator to be installed into various kinds of cars, as far as possible, however according to the conventional arts 1 and 2 mentioned above, sizes of the alternator for use in the vehicle as a whole, in particular, an outer diameter thereof comes to be large, since the passages for coolant are formed so as to enclose all around of the stator, therefore it is difficult to fit the alternator suitable for the restricted space where it should be installed into. Also, for the purpose of fitting to various kinds of cars, it is necessary to change over the housing and the front and rear brackets thereof, but it brings about a problem that the alternator is low in mass-productivity thereof.
A first object, according to the present invention, is to provide an alternator for use in an automobile, having low noises and enabling the stator and the rotor to be cooled down effectively, thereby obtaining a high output therefrom.
A second object, according to the present invention, is to provide an alternator for use in a vehicle, enabling the standardization to be fitted for various kinds of cars, as well as, being suitable for coping with restriction of the space where it is installed, thereby being superior in the mass-productivity.
For accomplishing the first object mentioned above, according to the present invention, there is provided an alternator for use in a vehicle, comprising: a stator having a stator core being formed in a cylindrical shape and a stator coil wound around said stator core; a rotor having pole cores and an excitation coil, being attached on a rotation shaft, so as to be located within said stator; brackets, being thermally connected to said stator for supporting said stator, for supporting said rotation shaft at both sides of said rotor, and being closed at one side of said rotor; cooling liquid passages provided in said brackets; a cooling fan provided at the closing side of said rotor; and a cooling fin provided in vicinity of said cooling passages, opposing to said cooling fan.
For accomplishing the second object mentioned above, according to the present invention, there is provided an alternator for use in a vehicle, comprising: a rotation shaft, on which rotating power is transmitted from an engine of a vehicle through a pulley; a rotor fixed on to said rotation shaft, to be excited by an excitation coil; a stator provided in an outer periphery of the rotor, being wound around with a stator coil; a front bracket for supporting the stator in a direction of said rotor shaft from a side of the pulley, and for supporting said rotation shaft through a shaft bearing; and a rear bracket for supporting said stator from an opposing side of said pulley, and for supporting said rotation shaft through a shaft bearing, wherein either one of said front bracket and said rear bracket comprises: a cooling liquid passage extending in a peripheral direction thereof; and conduction member attachment portions, being formed in condition of being closed at plural number of positions around an outer periphery portion thereof, locating in an outside of said cooling liquid passage.